Seeds of success: seed biology and germination response of Gazania weed in Australia

Seed length did not vary across populations, but the seed width of a roadside population (Pop-1) was significantly less (37%) than a population from a cropping field (Pop-3). Germination response was same (>90%) in alternating light/dark (14/10 h) or complete dark (24 h) conditions. All populations had >78% germination across a wide range of alternating day/night temperatures (15/5, 25/15, and 35/25°C).

Populations did not differ in their germination response to moisture stress. Seeds did not germinate beyond -1.2 MPa water potential, while 50% germination inhibition occurred at -0.67 MPa. Gazania seeds could germinate up to a high salinity level of 300 mM of sodium chloride.

Population 1 was more tolerant to salinity than Pop-3 with a 50% reduction in germination occurring at 268 and 252 mM NaCl, respectively. The pH did not affect germination irrespective of the population. Less seeds could emerge from soil (32%) compared to sand (62%) and potting mix (69%).

Seedling emergence and root length decreased with increasing burial depth and no emergence was observed at 6 cm depth. However, these results represent a single population tested in burial depth study. Despite some population variations, gazania has flexible germination requirements potentially enabling their invasion.<p></p>